1. Field of the Invention
This invention relates to a regulated power supply system arranged to provide unidirectional current to at least one load at an output voltage that remains substantially constant despite variation in load current within a predetermined range.
2. Description of the Prior Art
Regulated power supply systems are known in which a load is fed with unidirectional current by way of a switch operated with a duty cycle such that the voltage applied to the load remains substantially constant during variation of the load current, at least within a predetermined range.
In power supply systems of this kind, the voltage regulating devices commonly take the form of switches, the mode of control being such that the ratio of the "on" period of the switch to its "off" period (its duty cycle) is varied so that the switch output, when time-averaged by means of a low-pass filter, provides a unidirectional output of a desired voltage. It is a disadvantage of commonly-used solid-state switches, for example, transistors, is that there is a small but unavoidable forward voltage drop across the switch when in its conductive condition, which may give rise to severe problems of power loss and necessary heat dissipation at the high output currents required in many applications. Also it has been usual to derive a plurality of distinct unidirectional supplies from a voltage divider connected across a common unidirectional current supply and it is a disadvantage of a system of this kind that it gives rise to interaction between the plurality of loads energized from the common supply.